This is annoying and has been happening since I completed the main quest. I do have several mods - such as Imps More Complex Needs and Belua Sanguinaire.

I tried deactivating all of my mods, and the screenshots (except for one of them that I took earlier) were taken with the glow still on.

I already tried waiting 30 in-game days.

I am not sure what is causing this but how can I fix it? It's very annoying, especially since my character is a vampire who is supposed to hide perfectly in the shadows, NOT glow like some sort of angel.

In the following screenshots I show what this glow is exactly. I don't know what is causing it, it might be a fortify effect or something to do with the Restoration school. It is similar to the glow a character has when healing oneself. He is naked in all screenshots to show that nothing he is equipping is causing this problem.

In first person view, this is what is shown below me. My weapons glow as well.

Sometimes I appear as a cloud of dust and glow when invisible. This is the screenshot taken when I had all mods activated.

This shows my character invisible. Sometimes there is no cloud but just the geometry glows.

And here is my character.

I used to notice an odd glow around my character on the Xbox 360 version. Nothing like yours however. It was like a 3 inch, glowing, clear outline all around my character. I haven't noticed it recently though.

Unfortunately, desactivating your mods is not enough; you must uninstall them completely. Remove all the things they add: textures, scripts, etc. While you're at it, delete the Skyrim.ini and the SkyrimPrefs.ini that are in My Documents/My Games/Skyrim. If the glow effect is still there once you've done that...